Electrically-wound clock



Dec. 23, 1930. CAMPBELL 1,786,288

ELECTRICALLY WOUND CLOCK Filed Feb. 28. 1929 I Inventor: Arthur B.Campbell.

- His At'tofiriey.

Patented Dec. 23, 1930 UNITED STATES PATIENT OFFICE- ARTHUR B. CAMPBELL, OF FORT WAYNE, INDIANA, ASSIGNORTO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK V ELECTRICALLY-WOUND CLOCK Application filed February 28, 1929. Serial No. 343,366.

My invention relates to a constant torque power transmission mechanism which is suitable. for general'application but which is particularly adapted for use in spring driven clock movements where a small electric motor is employed for winding the spring.

The time keeping qualities of the ordinary hand wound spring driven clock movement are impaired by reason of the fact that the clock escapement is required to regulate the speed between wide limits of the main spring tension. In the eight-day clock for example, when the spring is fully Wound. the escapement mechanism is subjected to considerably more tension'than exists when the spring is nearly unwound. As a result the beat of the escapement tends to vary somewhat with the tension of the main spring. This varying condition may be compensated for to some extent but at the expense of added complications and cost. To avoid the conditions above mentioned it has been proposed to maintain the clock spring wound to a substantially constant tension by automatic means, such.

asan electric motor, together with means dependent on thecondition of the spring for controlling the motor.

My invention relates to improvements in devices of the last mentioned group and its principal object is to provide a simple-inexpensive but reliable mechanism for maintaining the clock springwound to a very uniform tension. In carrying myinvention' into efiect I provide means responsive to the counter torque of the main spring for-controlling the winding torque transmitted thereto from the winding motor.

In its broader aspect my invention relates to a mechanical power transmission system in which there are a pair of rotatably mounted intermeshed gear wheels through which power is transmitted. One of the gears is mounted for limited'bodily movement with respect to the other in substantially a tangential direction. When power is transmitted between the gears it tends to cause a bodily movement of the last mentioned gear. Resilient means are provided opposing such movement such that the extent of the move- -ment'becomes proportional to the power ible.

transmitted at any given speed or proportional to the torque between such gears. I then provide means responsive to such movement for controlling the torque transmitted through these gear In the preferred form of my invention, I provide the bodily movable or floating gear closely adjacent the spring in a gear train connected between the motor and the clock spring. The floating'action of the gear is made'proportional to the torque being transmitted through it from the motor to the clock spring and actuates a control device for the motor such as a friction brake so as to maintain the spring Winding torque constant and the spring wound to a desired predetermined tension. This type of control is simple, noiseless and effective.

The features of my invention which are believed to be novel and patentable will he pointed out in the claims appended hereto.

For a better understanding of my invention sentation of an electrically wound clock movement equipped with a preferred form of my invention, and Fig. 2 is an explanatory diagram showing the regulating device in 53110131101 position from that represented in In the drawing, 10 represents the stationary shaded coil field member and 11 the rotary disc of a usual type of alternating current induction motor. The motor is intended to be normally constantly energized. The disc armature 11 is mounted on a shaft 12 carrying a worm 13 meshing with a pinion 14. Such a worm gear drive is irrevers- By this I mean that torque may be transmitted from 13 to 14 but any attempt to drive shaft 12 from gear 14 through the worm merely locks the gear 14 and produces no rotation of shaft 12. Gear 14 drives a shaft 15 and pinion 16. Pinion 16 meshes .with and drives a gear 17 mounted on a long the motor as explained hereinafter. Within the barrel 21' is a clock spring 21 one end of which is fastened to the barrel and the other end to a shaft 22 leading to the clock pointers 23 and the necessary reduction gears represented at 24 and through gear 25 and gear train 26 to the clock escapement 27. The clock mechanism which is driven by the spring may be of any type and may include provisions for setting the pointers, driving a second hand, etc., which are unnecessary to describe here, it being understood that the drawing is merely intended to illustrate the more essential parts of such a mechanism.

If we assume that the shaft 18 is rotatably mounted at both ends in fixed bearings and no other provision is made for controlling the spring, the motor upon being energized will wind up the clock springto a tension dependent solely on the torque of the motor. The motor torque is subject to more or less variation due for example to changes in temperature and variations in the voltage and the frequency of the source of supply. Unless suitable torque controlling means are rovided the variations in motor torque will be conveyed to the spring and result in a variation in its winding tension.

Accurate time keeping qualities of a clock mechanism such as is here described depend in part upon a constant spring tension, and the object of the floating gear 19 and the parts associated therewith is to maintain the winding torque constant regardless of varia-- tions in the motor torque. To accomplish this result in a simple manner the following arrangement is preferred. The bearing for the left hand end of shaft 18 is contained in a movable lever 28. Lever28 is pivoted at a point 29 substantially in alinement with the axis of rotation of gears 20 and 19. The movement of lever 28 is limited in one directionby a stop pin 30 and in the other direction by a spring 31 having one end hooked over the lever at 32 and the other end secured to an adjustable pin 33. This spring is tensioned so as to press lever 28 towards stop 30. The right hand end of shaft 18 is supported in a stationary bearing in the framework'as at 34; in such manner that the left hand end with gear 19 may be freely moved up and down a limited amount. The shaft 18 is of suflicient length and the gear 17 sufliciently close to the bearing 34 that this movement does not interfere with the mesh of gears 16 and 17 or cause binding under any operating condition.

The direction of rotation of the gears for winding the clock spring is indicated by arrows and is such that the torque transmitted between gear 19 and gear 20 tends to lift gear 19 against the action of spring 31. As a result the up and down floating action or position of lever 28 andgear 19 varies with the counter torque or winding tension of the preferably clock spring 21. This floating action is made use of to control the motor so that the torque transmitted between gears 19 and 20 remains substantially constant regardless of variations in the torque of-tlie motor. This is accomplished by a friction brake pad 35 mounted on a brake arm 36 attached to lever 28, which brake ad is brought against the motor disc 11 y the upward movement of lever 28. In the arrangement shown, the brake arm extends downward around the edge of the disc armature so as to bring the brake pad closely adjacent to and beneath the lower edge of the disc armature. The parts are adjusted so that when the arm 28' is against stop pin 30 the brake pad is not in contact with the disc but when the clock spring is wound to the desired tension the pad moves in contact with the disc and places a brake on the motor. The desired clock spring windin tension may be very accurately adjusted y adjusting the tension of spring 31 as by shifting the position of the pin 33 (see Fig. 2).

Fig. 2 represents the relative position of the parts with the brake pad against the. motor disc 11.

This provides a very effective and accurate regulator since when the desired clock spring tension is reached rotation of the floating gear 19 merely causes the same to climb up on gear 20 instead of driving it until the rotational movement is stoppedor slowed down by the braking action. I do not mean to imply that this controlling action is abrupt or that the brake is suddenly applied. The floating gear takes a position where the brake is partially applied permitting the constantly energized motor to rotate just fast enough to maintain the clock spring wound to a constant tension. In actual operation, with the clock spring wound up, and the clock in operation, the motor disc may make a few revolutions and then stop for a few seconds. The torque measurement which determines when the application of the brake is made is at that portion of the driving train which is closest to the clock spring and as a result the controlling action is made in response to a very accurate measurement of the clock spring tension" and a highly accurate regulation results.

The clock spring is preferably of sufficient length to maintain the clock in operation for an appreciable time interval such as'several hours in case the power sup ly should fail. In such cases the irreversi le wound gear drive between the motor shaft. and gear train prevents the clock spring from unwinding by driving the motor backward.

The details and arrangement of parts may be modified. The control is useful for devices other than spring driven electrically wound clocks. It is not absolutely essential that the floating gear placedznextto a spring barrel in the gear train or'that the motor be of the alternating current induction disc type. The appended claims are intended to cover all modifications and applications of my invention coming fairly within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States, 1s:

1. In a mechanical power transmission system, a pair of rotatably mounted intermeshed spur gear wheels through which power 'is transmitted, one of said gears being mounted for limited bodily movement with respect to the other in substantially a tangential direction, resilient means for opposing such bodily movement occasioned by the transmission of power between said wheels, and means controlled by such bodilymovement for maintaining the torquebetween said gears substantially constant.

2. In a power transmission system, a rotatably mounted shaft having gear wheels adjacent opposite ends through which power is transmitted, other gear wheels meshing with the gears on said shaft, one end of said shaft having a bearing in a stationary member and the other end having a bearing in a member which permits the gear wheel at that end to move bodily in substantially a tangential direction with respect to the I gear with which it meshes, the amount of resilient means opposing such bodily movesuch movement and the length of the shaft being such as to maintain proper driving relation between all the intermeshed gears,

ment which is caused by the transmission of power through such gear train whereby the extent of such movement becomes proportional to the torque between intermeshed gears, and means controlled by such movement for controlling the power transmitted therethrough.

3.. In a mechanical power transmission systerm, a pair of rotatably mounted inter-meshed spur gear wheels through which power is transmitted one of said gears being mounted for limited bodily movement with respect to the other in substantially a tangential direction, resilient means for opposing such movement, a motor supplying mechanical power through said gears in a direction tending to through which said spring is wound, said gear train including a pair of intermeshed spur gear wheels one of which is bodily movable in substantially a tangential direction with respect to the other, resilient means for opposing such bodily movement, the direction of rotation of said gears being such that the torque betiveen'sa'id gears occasioned by the winding of the spring causes thebodily movable gear to move in opposition to the resilient means whereby such movement becomes pro port-ional to the counter torque or tension of the spring, and means controlled by such movement for limiting the torque between said gears.

5. In a mechanical power transmission system, a rotatably mounted shaft having gear wheels adjacent opposite ends through which power is-transmitted, a gear train including other gear wheels meshing with the gears on said shaft, one end of said shaft having a bearing in a stationary member and the other end having a bearing in a member which permits the gear wheel at that end to move bodily in substantially a tangential direction with respect to the gear with which it meshes, the amount of such movement and length of the shaft being such as to maintain proper driving relation between the intermeshed gears, resilient means opposing such bodily movement caused by the transmission of power through said gear train, a spring, the bodily movable gear being connected through the gear in mesh therewith to wind said spring when power is transmitted through said gears, a motor for supplying driving power to said gearrtrain for winding said spring, a

friction brake for said motor, and means for causing the application of said brake in response'to the bodily movement of the bodily movable gear whereby the winding torque to said spring is maintained below a predetermined amount.

6. A movement, a spri n for driving said movement, an escapement or controlling the rate at which the movement is driven by the spring, a normally constantly energized electric motor, a gear train connected between said motor and spring for winding the latter,

.said gear train including a pair of intermeshed spur gear wheels one of which is bodily movable in substantially a tangential direction with respect to the other in response to the torque transmitted therethrough, and means for controlling the speed of said motor in response to the bodily movement of the bodily movable gear to maintain constant the winding tension of said spring.

7. A movement, a spring for driving said movement, an escapement for controlling the rate at which the movement is driven by said spring, said spring, when wound to a desired predetermined tension, being capable of driv.- ing said movement for an appreciable interval of time without rewinding, a normally consta-ntly ener 'zed electric motor, a gear train connecte between said motor and spring for winding the latter, the motor as thus connected being capable of winding said spring beyond said desired predetermined tension, said gear train including an irreversible worm and pinion drive whereby the spring is prevented from driving the motor backward to unwind the spring in case the power supply to the motor should fail, said gear train also including a pair of intermeshed spur gear wheels closely adjacent the spring end of the train, one of which gear wheels is b'odily'movable in substantially a tangential direction with respect to the other a limited amount in response to the winding torque of the spring transmitted therethrough, and means for controlling the motor in response to such bodily movement to normally maintain the spring wound to said desired predetermined tension.

In witness whereof, I havehereunto set my hand this 26 day of Feb., 1929.

ARTHUR B. CAMPBELL. 

